HEMODYNAMIC EFFECTS OF VARIOUS MODES OF CARDIAC PACING AFTER OPERATION FOR IDIOPATHIC HYPERTROPHIC SUB-AORTIC STENOSIS

The hemodynamic effects of varying heart rate and pacing site were studied in 6 patients with idiopathic hypertrophic subaortic stenosis following operative relief of outflow obstruction. Ventricular pacing (117 beats per minute) resulted in a 26% decrease in cardiac output (p < 0.02), a 54% increase in pulmonary capillary wedge pressure (p < 0.03), and a 23% decrease in mean blood pressure (p < 0.05), compared with normal sinus rhythm (88 beats per minute). Slow atrial pacing (112 beats per minute) did not significantly alter any hemodynamic variable compared with normal sinus rhythm. Rapid atrial pacing (143 beats per minute) produced a similar degree of hemodynamic impairment as ventricular pacing. This study demonstrates that ventricular pacing at heart rates commonly used clinically and rapid atrial rates result in a significant fall in cardiac output. Preservation of atrial systole at heart rates that allow adequate diastolic ventricular filling of a hypertrophied, non-compliant ventricle is stressed. In addition, atrial electrodes are useful to record atrial electrograms or induce rapid atrial stimulation to treat supraventricular tachyarrhythmias. © 1979, The Society of Thoracic Surgeons. All rights reserved.